Error code 5300:0119

I hope someone can help, I have run a diagnostics from the Utility partition and this is one of the codes that comes up.  I understand it is something to do with the video memory.  I have a Dimension 5150 with a 256Mb ATI Radeon  graphics card.  I don't know if this is referring to the memory onboard the motherboard or the meory on the graphics card?

In normal operatioon of the PC (i.e displaying internet web pages) the display is fine, but the screensaver seems to have a chequreboard effect, and games won't display properly (missing graphics, reduced colours) I have tried flashing the BIOS and re-installing drivers for onboard Intel and the ATI and this has made no difference

Any assistance/advice/guidance would be greatly appreciated.